I just bought the US Robotics 5630B External Hard modem. At first I had some problems with it under Linux (my OS is Mandrake 10.1). I started to search information how to initialaze it and found your message that it does not work in Linux. I was very sad. But I was told that hard modem must work. So I visited several Russian forums where I am from and got the answer.
1. At first you have to configure your COM-port. The best way for it to use minicom program. You have to set the baud rate of the COM-port 115200 and you have to have UART at least 16550A (details are here
http://tldp.org/HOWTO/Modem-HOWTO.html ).
2. Then you have to configure your kppp program in this way:
a) authorisation PAP/CHAP
b) device: /dev/ttyS* (your COM-port, may be /dev/ttyS0), [CRTSCTS], CR/LF, 115200, use lock-file -yes, timeout of modem - 120 s;
c) modem: commands (most important!): change only init string 1 to:
AT&F1&B1&A3E0Q0V1&C1&D2&P1S0=0
(this is very specific string was found in .inf file of Windows driver on the CD that was in the box; perhaps the settings fot your country can be different, let you see the Windows driver init string, init 1 or init 2, if init 1 is just AT command). You have to choice also ATDT or ATDP.
d) different: timeout of pppd I would reccomend to set at least 30 sec.
It works correctly. I have the good speed 50K and very stable connection.
So I found that we can use the information from Win-drivers.
Have good use of the modem.
Regards, Dmitry, Saint-Petersburg
U.S. Robotics and wvdial pucanje daemon